The serine/threonine protein kinase ROCK consists in humans of two isoforms ROCK I and ROCK II. ROCK I is encoded on chromosome 18 whereas ROCK II, also called Rho-kinase, is located on chromosome 12. They both have a molecular weight close to 160 kDa. They share an overall homology of 65% while being 95% homologous in their kinase domains. Despite their sequence similarity, they differ by their tissue distributions. The highest levels of expression for ROCK I are observed in heart, lung and skeletal tissues whereas ROCK II is mostly expressed in brain. Recent data indicate that these two isoforms are partially function redundant, ROCK I being more involved in immunological events, ROCK II in smooth muscle function. The term ROCK refers to ROCK I (ROK-β, p160ROCK, or Rho-kinase β) and ROCK II (ROCK-α or Rho-kinase α).
ROCK activity has been shown to be enhanced by GTPase RhoA that is a member of the Rho (Ras homologous) GTP-binding proteins. The active GTP-bound state of RhoA interacts with Rho-binding domain (RBD) of ROCK that is located in an autoinhibitory carboxyl-terminal loop. Upon binding, the interactions between the ROCK negative regulatory domain and the kinase domain are disrupted. The process enables the kinase to acquire an open conformation in which it is fully active. The open conformation is also induced by the binding of lipid activators such as arachidonic acid to the PH domain in the kinase carboxyl-terminal domain. Another activation mechanism has been described during apoptosis and involves the cleavage of carboxyl terminus by caspase-3 and -2 (or granzyme B) for ROCK I and II, respectively.
ROCK plays an important role in various cellular functions such as smooth muscle contraction, actin cytoskeleton organization, platelet activation, downregulation of myosin phosphatase cell adhesion, -migration, -proliferation and survival, thrombin-induced responses of aortic smooth muscle cells, hypertrophy of cardiomyocytes, bronchial smooth muscle contraction, smooth muscle contraction and cytoskeletal reorganization of non-muscle cells, activation of volume-regulated anion channels, neurite retraction, wound healing, cell transformation and gene expression. ROCK also acts in several signaling pathways that are involved in auto-immunity and inflammation. ROCK has been shown to play a part in the activation of NF-κB, a critical molecule that leads to the production of TNF and other inflammatory cytokines. ROCK inhibitors are reported to act against TNF-alpha and IL-6 production in lipopolysaccharide (LPS)-stimulated THP-1 macrophages. Therefore, ROCK inhibitors provide a useful therapy to treat autoimmune and inflammatory diseases as well as oxidative stress.
In conclusion, ROCK is a major control point in smooth muscle cell function and a key signaling component involved in inflammatory processes in various inflammatory cells as well as fibrosis and remodeling in many diseased organs. There are clear indications that ROCK is involved in the pathogenesis of many diseases, including asthma, COPD and glaucoma. In addition, ROCK has been implicated in various diseases and disorders including eye diseases; airway diseases; cardiovascular and vascular diseases; inflammatory diseases; neurological and CNS disorders: proliferative diseases; kidney diseases; sexual dysfunction; blood diseases; bone diseases; diabetes; benign prostatic hyperplasia, transplant rejection, liver disease, systemic lupus erythmatosis, spasm, hypertension, chronic obstructive bladder disease, premature birth, infection, allergy, obesity, pancreatic disease and AIDS.
ROCK appears to be a safe target, as exemplified by knockout models and a large number of academic studies. These KO mice data, in combination with post-marketing surveillance studies with Fasudil, a moderately potent ROCK inhibitor used for the treatment of vasospasm after subarachnoid hemorrhage, indicate that ROCK is a genuine and significant drug target.
ROCK inhibitors would be useful as therapeutic agents for the treatment of disorders implicated in the ROCK pathway. Accordingly, there is a great need to develop ROCK inhibitors that are useful in treating various diseases or conditions associated with ROCK activation, particularly given the inadequate treatments currently available for the majority of these disorders. Some non-limiting examples are inflammatory bowel disease, ulcerative colitis, Crohn's disease, asthma, COPD, pulmonary hypertension and idiopathic pulmonary fibrosis.
Allergic asthma is a chronic inflammatory airway disorder that results from maladaptive immune responses to ubiquitous environmental proteins in genetically susceptible persons. Despite reasonably successful therapies, the prevalence increases as these therapies do not cure; there are still exacerbations and an increasing number of non-responders. New, effective and steroid-sparing treatments that tackle all components of the disease are required.
Chronic Obstructive Pulmonary Disease (COPD) represents a group of diseases characterized by irreversible limitation of airflow, associated with abnormal inflammatory response, bronchoconstriction and remodeling and destruction of the tissue of the lung. It is one of the leading causes of death worldwide, with a steadily increasing prevalence. There is an urgent need for novel therapeutic approaches as the current regimen is inadequate. Until recently, only bronchodilators were used, since glucocorticoids have limited or no effect. Roflumilast (Daxas, Dallresp) was approved in 2010 for the treatment of COPD, but is associated with several dose-limiting side effects. Reference ROCK inhibitors, such as Y-27632 relax human isolated bronchial preparations, inhibit increases in airway resistance in anaesthetised animals, potentiate relaxing effects of β-agonists in vitro and in vivo and give rapid bronchodilatation upon inhalation. In addition, ROCK inhibitors block tracheal smooth muscle contractions induced by H2O2, the clinical marker for oxidative stress.
Related to airway inflammation, ROCK inhibitors counteract the increase in trans-endothelial permeability mediated by inflammatory agents, maintain the endothelial barrier integrity, inhibit the influx of eosinophils after ovalbumin challenge in vivo, protect against lung edema formation and neutrophile migration, suppress airway HR to metacholine and serotonin in allergic mice and block LPS-induced TNF release. With respect to airway fibrosis and remodeling, ROCK inhibitors block the induced migration of airway smooth muscle cells. In vitro evidences for the role of ROCK in airway remodeling were obtained in human lung carcinoma cell line, bovine tracheal smooth muscle cells and human airway smooth muscle. In vivo proof for a role of ROCK in fibrosis in general was generated with mice which exhibited attenuated myocardial fibrosis in response to the partial deletion of ROCK. The attenuation of myocardial fibrosis by Y-27632 in response to myocardial infarction and by fasudil in the case of congestive heart failure in a chronic hypertensive rat model brings additional indications of ROCK's importance in remodeling. Finally, ROCK inhibitors increase apoptotic cell loss of smooth muscle cells.
Several different classes of ROCK inhibitors are known. The current focus is oncology and cardiovascular applications. Until now, the outstanding therapeutic potential of ROCK inhibitors has only been explored to a limited extent. The reason is the fact that ROCK is such a potent and widespread biochemical regulator, that systemic inhibition of ROCK leads to strong biological effects that are considered as being side effects for the treatment of most diseases. Indeed, the medical use of ROCK inhibitors to treat diseases with a strong inflammatory component is hampered by the pivotal role of ROCK in the regulation of the tonic phase of smooth muscle cell contraction. Systemically available ROCK inhibitors induce a marked decrease in blood pressure. Therefore, ROCK inhibitors with different properties are highly required.
For the target specific treatment of disorders by regulating smooth muscle function and/or inflammatory processes and/or remodeling, it is highly desired to deliver a ROCK inhibitor to the target organ and to avoid significant amounts of these drugs to enter other organs. Therefore, local or topical application is desired. Typically, topical administration of drugs has been applied for the treatment of airway-, eye, sexual dysfunction and skin disorders. In addition, local injection/infiltration into diseased tissues further extend the potential medical use of locally applied ROCK inhibitors. Given certain criteria are fulfilled; these local applications allow high drug concentration to be reached in the target tissue. In addition, the incorporation of ROCK inhibitors into implants and stents can further expand the medical application towards the local treatment of CV diseases such as atherosclerosis, coronary diseases and heart failure.
Despite the fact that direct local application is preferred in medical practice, there are concerns regarding drug levels reached into the systemic circulation. For example the treatment of airway diseases by local delivery by for instance inhalation, poses the risk of systemic exposure due to large amounts entering the GI tract and/or systemic absorption through the lungs. Also for dermal applications, local injections and implantable medical devices, there is a severe risk of leakage into the systemic circulation. Therefore, in addition to physical local application, the compounds should preferably have additional chemical or biological properties that will minimize systemic exposure.
Soft drugs are pharmacologically active compounds that are inactivated once they enter the systemic circulation. This inactivation can be achieved in the liver, but the preferred inactivation should occur in the blood. These compounds, once applied locally to the target tissue/organ exert their desired effect locally. When they leak out of this tissue into the systemic circulation, they are very rapidly inactivated. Thus, soft drugs of choice are sufficiently stable in the target tissue/organ to exert the desired biological effect, but are rapidly degraded in the blood to pharmacologically inactive compounds.
In conclusion, there is a continuing need to design and develop soft ROCK inhibitors for the treatment of a wide range of disease states. The compounds described herein and pharmaceutically acceptable compositions thereof are useful for treating or lessening the severity of a variety of disorders or conditions associated with ROCK activation. More specifically, the compounds of the invention are preferably used in the prevention and/or treatment of at least one disease or disorder, in which ROCK is involved, such as diseases linked to smooth muscle cell function, inflammation, fibrosis, excessive cell proliferation, excessive angiogenesis, hyperreactivity, barrier dysfunction, neurodegeration and remodeling. For example, the compounds of the invention may be used in the prevention and/or treatment of diseases and disorders such as:                Airway diseases; including but not limited to pulmonary fibrosis, emphysema, chronic bronchitis, asthma, fibrosis, pneumonia, cystic fibrosis, chronic obstructive pulmonary disease (COPD); bronchitis and rhinitis and respiratory distress syndrome,        Throat, Nose and Ear diseases: including but not limited to sinus problems, hearing problems, toothache, tonsillitis, ulcer and rhinitis,        Skin diseases: including but not limited to hyperkeratosis, parakeratosis, hypergranulosis, acanthosis, dyskeratosis, spongiosis and ulceration.        Intestinal diseases: including but not limited to inflammatory bowel disease (IBD), colitis, gastroenteritis, ileus, ileitis, appendicitis and Crohn's disease.        Cardiovascular and vascular diseases: including but not limited to, pulmonary hypertension and pulmonary vasoconstriction.        Inflammatory diseases: including but not limited to contact dermatitis, atopic dermatitis, psoriasis, rheumatoid arthritis, juvenile rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis, inflammatory bowel disease, Crohn's disease and ulcerative colitis.        Neurological disorders: including but not limited to neuropathic pain. The present compounds are therefore suitable for preventing neurodegeneration and stimulating neurogeneration in various neurological disorders.        Proliferative diseases: such as but not limited to cancer of, breast, colon, intestine, skin, head and neck, nerve, lung, pancreas, or thyroid gland; Castleman disease; malignoma; and melanoma.        Bone diseases: including but not limited to osteoporosis and osteoarthritis        In addition, the compounds of the invention may be used in the prevention and/or treatment of diseases and disorders such as benign prostatic hyperplasia, transplant rejection, spasm, chronic obstructive bladder disease, and allergy.        